During the first two seasons of Star Trek: The Next Generation, the crew of the Enterprise wore as their Starfleet uniforms zip-up spandex bodysuits. The actors hated them. They were smelly and tended to be a bit too, uh, form fitting. Patrick Stewart’s chiropractor told him that he might become permanently injured if he continued to wear the binding bodysuit. So Bob Blackman, a costume designer on multiple Star Trek series, designed new uniforms. In an interview, he explained the look that he was attempting to create:

At the beginning of that third season, you will see that the uniforms change structure during that time period, eventually ending up with that Eisenhoweresque mandarin collar, leaving the black yoke, leaving the angled colour panel on the front, but removing all of the piping that was on the yoke and all of that sort of thing, making them, essentially, more formal. Er, more dignity.

Some of that was necessary, because of Patrick, because of Americans and their sense of the English and the sound of an English accent. To make it more casual seemed inappropriate.